I would definitely agree with this. To be in a relationship with anyone there has to be a level of attraction. This is pretty universal whether you're BDSM or vanilla. However, not all subs will be attracted to the same type of guy. I don't think specifically that he has to look the part of Dom for there to be that level of attraction. I would go so far as to say the 'nice guys' will surprise you more when they assert their dominance and can get more of a reaction/response, at least initially.